CN1273721A - Device and method for cancelling code interference in CDMA communication system - Google Patents

Abstract

Provided are an apparatus and method for eliminating intersymbol interference in a receiver in a CDMA (Code Division Multiple Access) communication system using both orthogonal codes and quasi-orthogonal codes. In the receiver of the embodiment of the present invention, the channel estimator generates an estimated value of the pilot channel signal spread with an orthogonal code by despreading. The quasi-orthogonal channel receiver receives channel signals spread by quasi-orthogonal codes, despreads the channel signals, demodulates the despread channel signals using channel estimation values, and provides output. The interference estimator obtains the correlation value between the orthogonal code corresponding to the pilot channel and the quasi-orthogonal code corresponding to the quasi-orthogonal channel to estimate the interference of the pilot channel signal to the channel spread with the quasi-orthogonal code. The interference value of the signal. An interference canceller removes estimated interference from the output of the quasi-orthogonal channel receiver.

Description

Device and method for eliminating intersymbol interference in code division multiple access communication system

Background of the invention

1. Field of the invention

The present invention relates to a kind of device and method for eliminating code interference (code interference) in CDMA (Code Division Multiple Access) communication system, relate in particular to be used in orthogonal code and quasi-orthogonal code (QOC, quasi-orthogonal Codes) exist simultaneously to realize channelization in a CDMA communication system, an apparatus and method for eliminating mutual interference between orthogonal codes and quasi-orthogonal codes.

2. Description of related technologies

In a CDMA communication system, orthogonal codes provide orthogonal channelization in all coded channels, and the maximum number of usable coded channels is determined by the length of the longest orthogonal code. Walsh codes (Walsh codes) are typical orthogonal codes used in CDMA systems, therefore, any references to orthogonal codes below refer to Walsh codes. If an orthogonal channel with orthogonality is designated exclusively for one transmitter/receiver from call setup until call release, the number of available channels becomes very limited, and channels cannot be assigned to each user. In order to enable all users to use the CDMA system, quasi-orthogonal codes are used. Although they do not have complete orthogonality, they have the least loss of orthogonality compared to other codes.

In order to minimize the loss of orthogonality, XOR is performed with the longest orthogonal code used in the system and a quasi-orthogonal code mask as long as the longest orthogonal code to generate the quasi-orthogonal code Cross code. The generation of binary quasi-orthogonal code masks, the generation of quasi-orthogonal codes, and the use of quasi-orthogonal codes are described in US Patent Application Serial No. 09/149,924, filed September 9, 1998. The characteristic of the quasi-orthogonal code is that it can maintain the orthogonality between the orthogonal code symbols using the same quasi-orthogonal code mask, and make the orthogonality between the quasi-orthogonal codes using different quasi-orthogonal code masks Sex loss is minimal.

W

F1 XOR W

F2 XOR W

F3 XOR W

· ·

· ·

· ·

FM XOR W

Wherein, W=N×N Walsh matrix, Fi=1×N row vector.

(1). Hexadecimal (16-ary) quasi-orthogonal mask of size 512

F1＝77B4B477 774BB488 87BB4478 78BBBB78 77B44B88 774B4B7778444478 8744BB78

77B4B477 774BB488 87BB4478 78BBBB78 77B44B88 774B4B7778444478 8744BB78

F2＝7E4DDBE8 17244D7E D41871BD 428E18D4 D4E77142 BD8EE7D47EB2DB17 E824B27E

7E4DDBE8 17244D7E D41871BD 428E18D4 D4E77142BD8EE7D4 7EB2DB17 E824B27E

F3＝417214D87DB1281BEB274172D7E47DB1B17DE4D78DBED8141B28B17D 27EB8DBE

417214D8 7DB1281B EB274172 D7E47DB1 B17DE4D78DBED814 1B28B17D 27EB8DBE

F4＝144EE441B114BEE44EEBBEE4144E1BBE8D287D27D78DD87DD78D2782 72D77D27

144EE441 B114BEE4 4EEBBEE4 144E1BBE 8D287D27D78DD87D D78D2782 72D77D27

F5＝488B7B47 1DDED1ED B88474B7 EDD1DE1D 122EDE1D477B74B7 1DDE2E12 488B84B8

488B7B47 1DDED1ED B88474B7 EDD1DE1D 122EDE1D477B74B7 1DDE2E12 488B84B8

F6＝1DB78BDED17B47121D488B212E7BB8122E7B47ED1D4874DED17BB8ED 1DB77421

  1DB78BDE D17B4712 1D488B21 2E7BB812 2E7B47ED1D4874DE D17BB8ED 1DB77421

(2). Hexadecimal quasi-orthogonal mask of size 256

F1＝77B4B477 774BB488 87BB4478 78BBBB78 77B44B88 774B4B7778444478 8744BB78

F2＝7E4DDBE817244D7ED41871BD428E18D4D4277142BD8EE7D47EB2DB17 E824B27E

F3＝417214D87DB1281BEB274172D7E47DB1B17DE4D78DBED8141B28B17D 27EB8DBE

F4＝144EE441B114BEE44EEBBEE4144E1BBE8D287D27D78DD87DD78D2782 72D77D27

F5＝488B7B47 1DDED1ED B88474B7 EDD1DE1D 122EDE1D477B74B7 1DDE2E12 488B84B8

F6＝1DB78BDED17B47121D488B212E7BB8122E7B47ED1D4874DED17BB8ED 1DB77421

(3). 16-column quasi-orthogonal mask of size 128

F1＝17DBBD71 E8DB4271 17DBBD71 E8DB4271

F2＝72824EBE BEB17D72 72824EBE BEB17D72

F3＝2DEE87BB 8744D2EE 2DEE87BB 8744D2EE

(4). 64-column quasi-orthogonal mask of size 512

F1＝17DBBD71 E8DB4271

F2＝72824EBE BEB17D72

F3＝2DEE87BB 8744D2EE

The correlation values between quasi-orthogonal codes and Walsh codes generated using the quasi-orthogonal code masks described above are listed in Table 1.

Table 1 walsh yards 512 256 128 64 32 16 8 4 QOS 512 0,32 16 0,16 8 0, 8 4 0,4 2 256 - 16 0,16 8 0, 8 4 0,4 2 128 - - 0,16 8 0, 8 4 0,4 2 64 - - - 8 0, 8 4 0,4 2

A basic orthogonal code is defined as an orthogonal code that is X-ORed with a quasi-orthogonal code mask to produce a quasi-orthogonal code and indicates a Walsh code. Walsh codes can come from different layers of different lengths as long as they ensure orthogonal channelization in the coded channel. However, in order to fully utilize the cross-correlation properties given in Table 1, it is preferable to use the Walsh code of the lowest layer or the longest Walsh code as the basic orthogonal code. Here, the length of the basic orthogonal code is defined as L.

FIG. 1 is a functional block diagram of a transmitter in a CDMA communication system using the above-mentioned quasi-orthogonal codes. Referring to FIG. 1, reference numerals 140 and 170 represent typical channel encoders and interleavers. The signal mappers 112, 142, and 172 convert "0" and "1" of input data into signal levels "+1" and "-1", respectively. The demultiplexers 144 and 174 separate traffic channel data into I-channel data and Q-channel data for QPSK (Quadrature Phase Shift Keying) transmission. Demultiplexers 144 and 174 may be serial-to-parallel converters (SPCs). In the case of BPSK (Binary Phase Shift Keying) modulation of the traffic channel data, the demultiplexers 144 and 174 are omitted and the data is transmitted on one I channel and one Q channel.

The Walsh code symbol W #0 generator 116 generates the code Walsh code symbol W #0 as a basic orthogonal code to spread the pilot channel. The pilot channel is used for channel estimation in the receiver. Mixer 118 multiplies the output of Walsh code symbol W #0 generator 116 with the output of signal mapper 112 to carry out orthogonal spread spectrum to the pilot channel signal, and then the pilot channel signal after orthogonal spread spectrum The frequency channel signal is sent to the adder 162. Walsh code symbol W #A generator 146 generates Walsh code symbol W #A which is a basic orthogonal code. Mixers 148 and 158 multiply the output of Walsh code symbol W#A generator 146 with the I-channel data and Q-channel data received from demultiplexer 144 to produce a spread spectrum signal. Gain controllers 150 and 160 control the relative gain of the traffic channel relative to the pilot channel.

Walsh code symbol W #a generator 176 generates Walsh code symbol W #a which is a basic orthogonal code. The quasi-orthogonal code mask M#m generator 186 generates a quasi-orthogonal code mask for generating a quasi-orthogonal code from a basic orthogonal code. Mixers 178 and 188 multiply the outputs of Walsh code symbol W #a generator 176 and quasi-orthogonal code mask M #m generator 186, thereby generating the Quasi-orthogonal code symbol Q[m] #a, and mixers 178 and 188 also phase the quasi-orthogonal code symbol Q[m] with the I channel and Q channel data received from demultiplexer 174 Multiply, so that the quasi-orthogonal code symbol Q[m] is spread. Gain controllers 180 and 190 control the relative gain of the traffic channel spread with the quasi-orthogonal code relative to the pilot channel. Adders 162 and 192 add the I-channel signal and the Q-channel signal, respectively, and output S_I[n] and S_Q[n]. PN (Pseudo Noise, pseudo-random noise) code generator 120 generates two PN sequences PN_I[n] and PN_Q[n] for complex PN spreading. Complex PN spreader 130 then complex PN spreads the outputs of adders 162 and 192 with the output of PN code generator 120 .

(S_I[n]+jS_Q[n])(PN_I[n]+jPN_Q[n])

=(S_I[n]PN_I[n]-S_Q[n]PN_Q[n])+j(S_I[n]PN_Q[n]+S_Q[n]PN_I[n])

I channel signal (S_I[n]PN_I[n]-S_Q[n]PN_Q[n[) and Q channel signal (S_I[n]PN_Q[n]+S_Q[n]PN_I [n]) are applied to the inputs of low-pass filters (LPF) 164 and 194, respectively. Amplifiers 166 and 196 scale the transmit signal to the desired level. The carrier generator 122 generates a carrier necessary to up-convert the frequency of the transmission signal to a high frequency. The 90° phase shifter 124 produces a 90° phase difference between the I channel and the Q channel. Mixers 168 and 198 multiply the outputs of amplifiers 166 and 196 by a carrier to modulate the transmit signal. Adder 126 adds the modulated I-channel and Q-channel signals, and transmit antenna 128 transmits the output of adder 126 .

Figure 2 is a block diagram of a conventional receiver in a CDMA system using quasi-orthogonal codes. Receive antenna 228 receives the modulated signal from the transmitter. Carrier generator 222 generates the carrier needed to down-convert the frequency of the received signal to the base frequency. The 90° phase shifter 224 produces a 90° phase difference between the I channel and the Q channel. Mixers 268 and 298 multiply the received signal by a carrier wave for demodulation, and then LPFs 264 and 294 filter out high-frequency components generated during demodulation, and only pass baseband signals.

Generally, in a mobile radio communication environment, there are a plurality of paths through which a signal transmitted from a transmitter can reach a receiver. However, the signal receiving mechanism is identical for each path.

Therefore, the signal receiving mechanism will be described here according to one path.

A PN (Pseudorandom Noise) code generator 220 generates PN sequences PN_I[n] and PN_Q[n] synchronized with the demodulated received signal. The complex PN despreader 230 calculates the low-pass filtered signal and the PN sequence with the following algorithm steps:

(S_I[n]PN_I[n]-S_Q[n]PN_Q[n])+j(S_I[n]PN_Q[n]+S_Q[n]PN_I[n])

(PN_I[n]+jPN_Q[n])

=(S_I[n]+jS_Q[n])(PN_I[n]+jPN_Q[n])(PN_I[n]+jPN_Q[n])

=S_I[n]+jS_Q[n]

Channel estimator 210 performs channel estimation for each path using a pilot channel spread by Walsh code symbol W #0. Walsh code symbol W #0 generator 216 generates Walsh code symbol W #0. Mixer 214 complex multiplies the output of complex PN despreader 230 and the output of Walsh code symbol W #0 generator 216. The accumulator 212 accumulates the output of the mixer 214 every predetermined time period to extract a channel estimation value. For this reason, the accumulator 212 can be replaced by an LPF. The channel estimate is used to demodulate the traffic channel. The data of the traffic channel can be obtained by multiplying the output of the complex PN despreader 230 by the quasi-orthogonal code symbol Q[m] #a for the traffic channel.

Mixer 254 multiplies the output of Walsh code symbol W #a generator 276 with the output of quasi-orthogonal code mask M#m generator 286 to produce quasi-orthogonal code symbol Q[m]# a, then, the quasi-orthogonal code symbol Q[m] #a is multiplied with the output of the complex PN despreader 230. Delay 250 delays the output of accumulator 252 by the time required for channel estimation in channel estimator 210 . Complex conjugator 206 generates the complex conjugate of the channel estimate received from channel estimator 210 for demodulation. Mixer 204 multiplies the complex conjugate of the channel estimate with the output of delay 250 to produce a demodulated signal.

The combiner 202 combines the multipath signals demodulated by the receiving mechanism. The deinterleaver and channel decoder 200 performs deinterleaving and channel decoding on the output of the combiner 202 .

Due to the coexistence of orthogonal codes and quasi-orthogonal codes, the above-mentioned conventional receiver suffers from a loss of orthogonality between channels. Therefore, it is impossible to reduce mutual interference between orthogonal codes and quasi-orthogonal codes.

Summary of the invention

An object of the present invention is to provide an apparatus and method for canceling interference of a signal received by a receiver in a CDMA communication system.

Another object of the present invention is to provide a CDMA communication system in which orthogonal codes and quasi-orthogonal codes coexist to eliminate the orthogonal codes and quasi-orthogonal codes caused by the loss of the orthogonality of the signal received by the receiver. Means and methods of interference.

Another object of the present invention is to provide a CDMA communication system in which orthogonal codes and quasi-orthogonal codes coexist to eliminate the interference between quasi-orthogonal codes and orthogonal codes caused by the loss of the orthogonality of the signal received by the receiver. Means and methods of interference.

To achieve the above objects, a receiver is provided in a CDMA communication system using both orthogonal codes and quasi-orthogonal codes. In a receiver according to an embodiment of the present invention, a channel estimator generates a channel estimation value of a pilot channel signal spread with an orthogonal code by despreading. The quasi-orthogonal channel receiver receives the channel signal spread by the quasi-orthogonal code, despreads the channel signal, and then demodulates the despread channel signal by using the channel estimation value, and provides an output. The interference estimator estimates the effect of the pilot channel signal on the channel signal spread with the quasi-orthogonal code by obtaining the correlation value between the orthogonal code corresponding to the pilot channel and the quasi-orthogonal code corresponding to the quasi-orthogonal channel interference value. An interference canceller removes estimated interference from the output of the quasi-orthogonal channel receiver.

A brief description of the drawings

By describing in detail preferred embodiments of the present invention in conjunction with the accompanying drawings, the above-mentioned purpose and advantages of the present invention will become more clear, wherein:

Fig. 1 is the block diagram of the prior art transmitter in the CDMA communication system using orthogonal code and quasi-orthogonal code;

Fig. 2 is the block diagram of the prior art receiver in the CDMA communication system using orthogonal code and quasi-orthogonal code;

Fig. 3 is, according to the first embodiment of the present invention, be used for canceling the block diagram of the receiver of the interference of the pilot channel that spreads with the orthogonal code to the traffic channel that spreads with the quasi-orthogonal code;

4 is a block diagram of a receiver for eliminating the interference of a pilot channel spread with an orthogonal code to a traffic channel spread with a quasi-orthogonal code according to a second embodiment of the present invention;

Fig. 5 is, according to the third embodiment of the present invention, be used for canceling the block diagram of the receiver of the interference of the channel that uses orthogonal code spread spectrum to the traffic channel that uses quasi-orthogonal code spread spectrum; And

6 is a block diagram of a receiver for canceling interference of a channel spread with a quasi-orthogonal code to a traffic channel spread with an orthogonal code according to a fourth embodiment of the present invention.

Detailed description of the preferred embodiment

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. In the drawings, the same reference numerals represent the same components.

The receiver of the invention can simultaneously use the orthogonal code and the quasi-orthogonal code in the CDMA communication system, and can eliminate the interference between the orthogonal code and the quasi-orthogonal code. All transmitters in the CDMA system use the same transmission power, the quality of reception can be improved, and the quality of reception can be maintained by reducing the transmission power of the transmitter.

Fig. 3 is, according to the first embodiment of the present invention, be used for canceling the block diagram of the receiver of the interference of the pilot channel that spreads with the orthogonal code to the traffic channel that spreads with the quasi-orthogonal code;

As described in the Background of the Invention section, receive antenna 228 receives the modulated signal from the transmitter. Carrier generator 222 generates the carrier needed to down-convert the frequency of the received signal to baseband frequency. The 90° phase shifter 224 produces a 90° phase difference between the I signal and the Q channel. Mixers 268 and 298 multiply the received signal by a carrier for demodulation. Then, LPF264 and 294 remove the high-frequency components generated during demodulation, and only let the baseband signal pass.

Generally, in a mobile radio communication environment, there are a plurality of paths through which a signal transmitted from a transmitter can reach a receiver. However, the signal receiving mechanism is identical for each path.

Therefore, the signal receiving mechanism will be described here according to one path.

The PN code generator 220 generates PN sequences PN_I[n] and PN_Q[n] synchronized with the demodulated received signal. The complex PN despreader 230 calculates the low-pass filtered signal and the PN sequence with the following algorithm steps:

(S_I[n]PN_I[n]-S_Q[n]PN_Q[n])+j(S_I[n]PN_Q[n]+S_Q[n]PN_I[n])

(PN_I[n]+jPN_Q[n])

=(S_I[n]+jS_Q[n])(PN_I[n]+jPN_Q[n])(PN_I[n]+jPN_Q[n])

=S_I[n]+jS_Q[n]

Channel estimator 210 performs channel estimation for each path using a pilot channel spread by Walsh code symbol W #0. Walsh code symbol W #0 generator 216 generates Walsh code symbol W #0. Mixer 214 complex multiplies the output of complex PN despreader 230 and the output of Walsh code symbol W #0 generator 216. The accumulator 212 accumulates the output of the mixer 214 every predetermined time period to extract a channel estimation value. For this reason, the accumulator 212 can be replaced by an LPF. The channel estimate is used to demodulate the traffic channel. The data of the traffic channel can be obtained by multiplying the output of the complex PN despreader 230 by the quasi-orthogonal code symbol Q[m] #a for the traffic channel.

Mixer 254 multiplies the output of Walsh code symbol W #a generator 276 and the output of quasi-orthogonal code mask M #m generator 286 to produce quasi-orthogonal code symbol Q[m]# a, then, the quasi-orthogonal code symbol Q[m] #a is multiplied with the output of the complex PN despreader 230. The accumulator 252 accumulates the output of the mixer 254 in units of data symbols. Delay 250 delays the output of accumulator 252 by the time required for channel estimation in channel estimator 210 . Complex conjugator 206 generates the complex conjugate of the channel estimate received from channel estimator 210 for demodulation. Mixer 204 generates the demodulated signal by multiplying the complex conjugate of the channel estimate with the output of delayer 250 .

Mixer 310 generates the square of the channel estimate by multiplying the channel estimate by the complex conjugate to obtain the energy of the channel estimate. The mixer 310 multiplies the product of the channel estimate and the complex conjugate by -C _0, ^am , where C _0, ^am is the Walsh code symbol W #0 and the quasi-orthogonal code symbol Q[m] Correlation value between #a. The output of mixer 310 is the interference component of the channel using Walsh code symbol W #0 to the traffic channel using quasi-orthogonal code symbol Q[m] #a.

Adder 320 removes the estimate of interference from the demodulated traffic channel signal received by mixer 204 . Therefore, the effect of the adder 320 is to eliminate the interference of the pilot channel spread with the Walsh code symbol W #0 to the traffic channel spread with the quasi-orthogonal code symbol Q[m] #a, and then The interference-free signal is applied to the input of combiner 202 .

The combiner 202 combines the multipath signals demodulated by the receiving mechanism. The deinterleaver and channel decoder 200 performs deinterleaving and channel decoding on the output of the combiner 202 .

As described above, mixer 310 multiplies the channel estimate by its complex conjugate to produce the square of the channel estimate output from channel estimator 210, which is then multiplied by -C _0, ^am , where C _{0, a} ^m is defined as:

Formula 1: $C_{i,j}^m=\underset{k=0}{\overset{L-1}{\mathrm{\Σ}}}(W_{i,k}\&Center\; Dot;Q_{j,k}^m)=\underset{k=0}{\overset{L-1}{\mathrm{\Σ}}}[W_{i,k}\&Center\; Dot;\left(m_k^{m\·W_{j,k}}\right)]$

Adder 320 then removes the estimate of the channel-to-traffic channel interference from the demodulated traffic channel signal. The interference-free signal is output to combiner 202 as in the prior art. According to the first embodiment of the present invention, the receiver shown in FIG. 3 estimates the interference of the channel to the channel using the quasi-orthogonal code, and then cancels the estimated interference from the channel using the demodulated quasi-orthogonal code.

Except for the above-mentioned interference cancellation, the overall process performed by this receiver is the same as that of the receiver in FIG. 2 .

4 is a block diagram of a receiver for canceling interference of a pilot channel spread with an orthogonal code to a traffic channel spread with a quasi-orthogonal code according to a second embodiment of the present invention. The receiver in Fig. 4 is substantially the same in structure and operation as the receiver in Fig. 3, except that the former includes means 410 for directly deriving the square of the channel estimate from the channel estimate.

5 is a block diagram of a receiver for canceling interference of a channel spread with an orthogonal code to a traffic channel spread with a quasi-orthogonal code according to a third embodiment of the present invention. The receiver shown in FIG. 5 will be described below, focusing on the elimination of interference from channels using orthogonal codes to traffic channels using quasi-orthogonal codes. A description of the general operation of the receiver is omitted here.

A fast Hadamard transformer 530 calculates the output of the complex PN despreader 230 according to the following formula:

Formula 2: $({\mathrm{<figure-callout\; id="0"\; label="d"\; filenames="A9980108800191.png,A9980108800201.png"\; state="\{\{state\}\}">d</figure-callout>}}_0,{\mathrm{<figure-callout\; id="1"\; label="d"\; filenames="A9980108800191.png,A9980108800231.png"\; state="\{\{state\}\}">d</figure-callout>}}_1,\&CenterDot;\&CenterDot;\&CenterDot;,d_{L-1})=({\mathrm{<figure-callout\; id="0"\; label="r"\; filenames="A9980108800191.png,A9980108800201.png"\; state="\{\{state\}\}">r</figure-callout>}}_0,{\mathrm{<figure-callout\; id="1"\; label="r"\; filenames="A9980108800191.png,A9980108800231.png"\; state="\{\{state\}\}">r</figure-callout>}}_1,\&CenterDot;\&CenterDot;\&CenterDot;r_{L-1})\left[\begin{array}{cccc}{\mathrm{<figure-callout\; id="0"\; label="W"\; filenames="A9980108800191.png,A9980108800201.png"\; state="\{\{state\}\}">W</figure-callout>}}_{\mathrm{0,0}}& {\mathrm{<figure-callout\; id="1"\; label="W"\; filenames="A9980108800191.png,A9980108800231.png"\; state="\{\{state\}\}"><figure-callout\; id="0"\; label="W"\; filenames="A9980108800191.png,A9980108800201.png"\; state="\{\{state\}\}">W</figure-callout></figure-callout>}}_{\mathrm{1,0}}& \&Center\; Dot;\&Center\; Dot;\&Center\; Dot;& W_{L-\mathrm{1,0}}\\ {\mathrm{<figure-callout\; id="0"\; label="W"\; filenames="A9980108800191.png,A9980108800201.png"\; state="\{\{state\}\}">W</figure-callout>}}_{\mathrm{0,1}}& {\mathrm{<figure-callout\; id="1"\; label="W"\; filenames="A9980108800191.png,A9980108800231.png"\; state="\{\{state\}\}"><figure-callout\; id="1"\; label="W"\; filenames="A9980108800191.png,A9980108800231.png"\; state="\{\{state\}\}">W</figure-callout></figure-callout>}}_{\mathrm{1,1}}& \&CenterDot;\&Center\; Dot;\&Center\; Dot;& W_{L-\mathrm{1,1}}\\ \&CenterDot;& \&CenterDot;& \&Center\; Dot;& \&Center\; Dot;\\ \&Center\; Dot;& \&CenterDot;& \&CenterDot;& \&CenterDot;\\ {\mathrm{<figure-callout\; id="0"\; label="W"\; filenames="A9980108800191.png,A9980108800201.png"\; state="\{\{state\}\}">W</figure-callout>}}_{0,L-1}& {\mathrm{<figure-callout\; id="1"\; label="W"\; filenames="A9980108800191.png,A9980108800231.png"\; state="\{\{state\}\}">W</figure-callout>}}_{1,L-1}& \&CenterDot;\&CenterDot;\&CenterDot;& W_{L-1,L-1}\end{array}\right]$

In a CDMA communication system, not all basic orthogonal codes defined by Equation 2 are used. Therefore, noise is introduced in the output of the Fast Hadamard Transformer 530 for unused Walsh code symbol inputs. The value of the noise component is smaller than the value of the Walsh code symbol in use. Therefore, the decider 520 compares the output of the fast Hadamard converter 530 with a predetermined value θ, and if the former is smaller than the latter, decides that the former is noise. If the Walsh code symbol is smaller than the predetermined value θ, the value of the Walsh code symbol is determined to be 0, thereby reducing the influence of noise (if |d _i |<0, then d _i =0).

Then, the arithmetic unit 510 uses formula 3 to multiply the vector of the output of the determiner 520 by (-1) and the correlation between the quasi-orthogonal code Q[m] #a used for the traffic channel and its corresponding Walsh code Vector of products of values:

Formula 3:

Among them, m is the mask number of the quasi-orthogonal code, α is the basic orthogonal code used to generate the quasi-orthogonal code, and L is the length of the orthogonal code.

Mixer 310 multiplies the complex conjugate of the channel estimate received from complex conjugator 206 by the output of operator 510 . The output of the mixer is an estimate of the interference of multiple orthogonal code channels to a quasi-orthogonal code channel. Adder 320 then cancels the channel using Walsh codes from the traffic channel using quasi-orthogonal codes by adding the output of mixer 310 to the signal of the demodulated traffic channel received from mixer 204. interference. The signals of the traffic channels using quasi-orthogonal codes are then applied to the input of combiner 202 without interference.

6 is a block diagram of a receiver for canceling interference of a channel spread with a quasi-orthogonal code to a traffic channel spread with a Walsh code according to a fourth embodiment of the present invention.

In the receiver of FIG. 6, the quasi-orthogonal code mask generator 286 of FIG. 5 is absent, and the receiver is used to receive traffic channel information using Walsh codes. Fast Hadamard transformer 630 calculates the output of complex PN despreader 230 according to Equation 4:

Formula 4

As described above with respect to FIG. 5, not all quasi-orthogonal codes defined by Equation 4 are used by CDMA systems. Therefore, the output of the fast Hadamard transformer 630 for the unused Walsh code symbol input is caused by noise. The value of the noise component is smaller than the value of the quasi-orthogonal code symbol in use. Therefore, the determiner 620 compares the output of the fast Hadamard converter 630 with a predetermined value θ, and if the former is smaller than the latter, it is determined that the former is noise. If the quasi-orthogonal code symbol is smaller than the predetermined value θ, the value of the quasi-orthogonal code symbol is determined to be 0, thereby reducing the influence of noise (if |d _i ^m |<0, then d _i ^m =0 ).

Then, the operator 610 uses formula 5 to multiply the vector of the output of the determiner 620 by (-1) and the product of the correlation value between the Walsh code W# used for the traffic channel and its corresponding quasi-orthogonal code Vector:

Multiple quasi-orthogonal codes can be generated from one basic orthogonal code by using different quasi-orthogonal code masks. In the system, quasi-orthogonal codes can be used together with their respective corresponding orthogonal codes. If multiple quasi-orthogonal codes are used, the number of receiver mechanisms described above increases in proportion to the number of quasi-orthogonal code masks used. Thus, the adder 640 sums the product of (-1) and the estimated value of the interference of the channel using the quasi-orthogonal code to the traffic channel using the Wall code symbol W#A. Mixer 310 multiplies the output of adder 640 by the complex conjugate of the channel estimate received from complex conjugator 206 . Here, the output of the mixer 310 is the interference components of channels using quasi-orthogonal codes to their corresponding channels using orthogonal codes. The adder 320 then eliminates the channel pair using the quasi-orthogonal code using the Walsh code symbol W# by adding the output of the mixer 310 to the demodulated traffic channel signal received from the mixer 204. Interference of A's traffic channel. The uninterfered traffic channel signal is then applied to the combiner 202 input.

As described above, in a CDMA communication system in which orthogonal codes and quasi-orthogonal codes coexist, the receiver of the present invention detects the alignment of the orthogonal codes with the quasi-orthogonal codes due to the loss of orthogonality between channels, or The quasi-orthogonal code interferes with the orthogonal code and removes the interference from the corresponding channel. In this way, all transmitters use the same transmission power, and the receiver can also obtain better reception quality. Moreover, the same reception quality can still be achieved by reducing the transmit power of the transmitter.

Although the invention has been described in detail above with reference to specific embodiments, these are exemplary applications only. It should therefore be clearly understood that various changes may be made by those skilled in the art within the scope and spirit of the invention as defined by the appended claims.

Claims (15)

1. A receiver using orthogonal codes and quasi-orthogonal codes in a CDMA (Code Division Multiple Access) communication system, said receiver comprising: A channel estimator for generating channel estimates of pilot channel signals spread by orthogonal codes by despreading; A quasi-orthogonal channel receiver, configured to receive a channel signal spread by a quasi-orthogonal code, despread the channel signal, use the channel estimate to demodulate the despread channel signal, and provide an output; an interference estimator for estimating the pilot channel signal pair spread with the quasi-orthogonal code by obtaining a correlation value between the orthogonal code corresponding to the pilot channel and the quasi-orthogonal code corresponding to the quasi-orthogonal channel The interference value of the channel signal of frequency; and an interference canceller for removing estimated interference from the output of said quasi-orthogonal channel receiver. 2. The receiver of claim 1, wherein the interference canceller comprises: a complex conjugater for computing the complex conjugate of the output of the channel estimator; a first multiplier for multiplying the output of the channel estimator by a complex conjugate; and The second multiplier is used to estimate the interference value of the pilot channel to the orthogonal channel by multiplying the correlation value by the output of the first multiplier. 3. The receiver of claim 1, wherein the interference canceller comprises: a squarer for squaring the output of the channel estimator; and a multiplier for estimating the interference value of the pilot channel to the orthogonal channel by multiplying the correlation value by the output of the squarer. 4. The receiver according to claim 1, wherein the correlation value is calculated according to the following formula: $C_{i,j}^m=\underset{k=0}{\overset{L-1}{\mathrm{\&Sigma;}}}(W_{i,k}\&Center\; Dot;Q_{j,k}^m)=\underset{k=0}{\overset{L-1}{\mathrm{\&Sigma;}}}[W_{i,k}\&CenterDot;\left(m_k^{m\&Center\; Dot;W_{j,k}}\right)]$ where i is the Walsh code used for the pilot channel, j is the basic orthogonal code used to generate the quasi-orthogonal code, m is the quasi-orthogonal code mask, and L is the length of the orthogonal code. 5. A receiver using orthogonal codes and quasi-orthogonal codes in a CDMA (Code Division Multiple Access) communication system, said receiver comprising: PN (pseudo-random noise) despreader, is used for carrying out PN despreading to the received signal; A quasi-orthogonal channel receiver for despreading a PN despread signal with a quasi-orthogonal code; An interference estimator, for estimating the interference value of the orthogonal code to the orthogonal code channel according to the PN despread signal; and an interference canceller for removing estimated interference values from the output of said quasi-orthogonal channel receiver. 6. The receiver of claim 5, wherein the interference estimator comprises: A fast Hadamard transformer for detecting unused orthogonal code symbols and used orthogonal code symbols; A decider for comparing the output of the fast Hadamard transformer with a predetermined value and removing unused orthogonal code symbols; and An operator for multiplying the vector output by the determiner by the correlation value between the quasi-orthogonal code of the quasi-orthogonal channel and the corresponding orthogonal code to generate an estimate of the orthogonal code-aligned quasi-orthogonal code channel interference value. 7. The receiver of claim 6, wherein the fast Hadamard transformer detects unused orthogonal code symbols by the following formula: $(d_0,d_1,\&Center\; Dot;\&Center\; Dot;\&CenterDot;,d_{L-1})=(r_0,r_1,\&CenterDot;\&CenterDot;\&CenterDot;r_{L-1})\left[\begin{array}{cccc}{W}_{\mathrm{0,0}}& W_{\mathrm{1,0}}& \&CenterDot;\&Center\; Dot;\&CenterDot;& W_{L-\mathrm{1,0}}\\ W_{\mathrm{0,1}}& W_{\mathrm{1,1}}& \&Center\; Dot;\&Center\; Dot;\&Center\; Dot;& W_{L-\mathrm{1,1}}\\ \&Center\; Dot;& \&Center\; Dot;& \&Center\; Dot;& \&Center\; Dot;\\ \&Center\; Dot;& \&Center\; Dot;& \&Center\; Dot;& \&Center\; Dot;\\ W_{0,L-1}& W_{1,L-1}& \&CenterDot;\&CenterDot;\&CenterDot;& W_{L-1,L-1}\end{array}\right]$ And, the computing unit estimates the interference value by the following formula:

Among them, m is the mask number of the quasi-orthogonal code, α is the basic orthogonal code used to generate the quasi-orthogonal code, and L is the length of the orthogonal code. 8. The receiver of claim 6, wherein the interference canceller comprises: a multiplier for multiplying the output of the operator by the complex conjugate of the pilot channel estimate; and an adder for removing the output of the multiplier from the quasi-orthogonal channel receiver. 9. A receiver using orthogonal codes and quasi-orthogonal codes in a CDMA (Code Division Multiple Access) communication system, said receiver comprising: PN despreader, for carrying out PN despread to received signal; Orthogonal channel receiver, used for despreading the signal after PN despreading with orthogonal code; An interference estimator, used for estimating the interference value of the quasi-orthogonal code to the basic orthogonal code according to the PN despread signal; and an interference canceller for removing the estimated interference value from the output of the quadrature channel receiver. 10. The receiver of claim 9, wherein the interference estimator comprises: A fast Hadamard transformer is used to distinguish between unused orthogonal code symbols and used orthogonal code symbols by operating on quasi-orthogonal code symbols of the PN despread signal; A decider for comparing the output of the fast Hadamard transformer with a predetermined value, and removing unused orthogonal code symbols; and An operator for multiplying the vector output by the determiner by the vector of correlation values between the orthogonal codes of the orthogonal channel and the corresponding quasi-orthogonal codes to generate estimated interference values of the quasi-orthogonal codes. 11. The receiver of claim 10, wherein the fast Hadamard transformer detects unused orthogonal code symbols by the following formula;

And, the computing unit estimates the interference value by the following formula:

Wherein, m is the quasi-orthogonal code mask number, A is the orthogonal code used in the orthogonal code channel receiver, and L is the length of the orthogonal code. 12. The receiver of claim 10, wherein the interference canceller comprises: a multiplier for multiplying the output of the operator by the complex conjugate of the pilot channel estimate; and an adder for removing the output of the multiplier from said quadrature channel receiver. 13. A method for eliminating intersymbol interference in a receiver using orthogonal codes and quasi-orthogonal codes in a CDMA communication system, comprising the following steps: generating channel estimates of pilot channel signals spread by orthogonal codes by despreading; receiving a channel signal spread by a quasi-orthogonal code, despreading the channel signal, and demodulating the despreaded channel signal using the channel estimate; By obtaining the correlation value between the orthogonal code corresponding to the pilot channel and the quasi-orthogonal code corresponding to the quasi-orthogonal channel, the interference of the pilot channel signal to the channel signal spread by the quasi-orthogonal code is estimated value; and The estimated interference value is removed from the demodulated quasi-orthogonal despread channel signal. 14. A method for eliminating intersymbol interference in a receiver for simultaneously using orthogonal codes and quasi-orthogonal codes and receiving channel signals spread by quasi-orthogonal codes in a CDMA communication system, said method comprising the following steps: A device for performing fast Hadamard transform on the orthogonal code symbols of the PN despread signal is used to distinguish between unused orthogonal code symbols and used orthogonal code symbols. Carrying out the output of the device of fast Hadamard transform to the orthogonal code symbol is compared with predetermined value, and removes the orthogonal code that is not used; Multiply the vector of the signal with the unused orthogonal code symbol removed by the vector of the correlation value between the quasi-orthogonal code of the quasi-orthogonal channel signal and the corresponding orthogonal code, and generate the orthogonal code alignment an estimated interference value of the cross-channel signal; and The estimated interference value is removed from the quasi-orthogonal channel signal. 15. A method for eliminating intersymbol interference in a receiver for simultaneously using orthogonal codes and quasi-orthogonal codes and receiving channel signals spread by orthogonal codes in a CDMA communication system, comprising the following steps: Distinguishing between unused orthogonal codes and used orthogonal codes by means of performing fast Hadamard transform on the PN despread signal; comparing the output of the Fast Hadamard Transform with a predetermined value, and removing unused orthogonal code symbols; multiplying the vector of the signal with the unused orthogonal code removed by the vector of the correlation value between the orthogonal code of the orthogonal channel signal and the corresponding quasi-orthogonal code, and generating the quasi-orthogonal code pair for the orthogonal channel signal The estimated interference value of ; and removing the estimated interference value from the orthogonal channel signal.

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